1. Field of the Invention
The present invention relates to a display control device and a method of controlling the same. In particular, the present invention relates to a display control device having periods during which a display device is driven by different current driving capabilities, and a method of controlling the same.
2. Description of Related Art
In recent years, a liquid crystal display panel such as a TFT (Thin Film Transistor) display panel has been often used as a display device. In the liquid crystal display panel, data is displayed, in general, by driving pixels arranged in a lattice pattern by a gate driver and a source driver. The gate driver has the same number of outputs as the number of rows of the pixels of the liquid crystal display panel, and selects a row of the pixels where data is displayed. The source driver has the same number of outputs as the number of columns of the pixels of the liquid crystal display panel, and drives the source of pixels located in respective columns in accordance with the display data.
That is, in a liquid crystal display panel, an image is displayed on a row-by-row basis by driving pixels located in the row that is selected by the gate driver by the source driver in accordance with display data. Furthermore, the image is displayed throughout the screen by successively shifting the selected column. Japanese Unexamined Patent Application Publication No. 05-19719 discloses one example of the driving device for a liquid crystal display panel.
FIG. 9 shows a block diagram of a driving device 100 in related art disclosed in Japanese unexamined patent Application Publication No. 05-19719. As shown in FIG. 9, the driving device 100 in the relate art includes a liquid crystal display panel 103, and a source driver 101 and a gate driver 102 to drive the liquid crystal display panel 103.
Pixels are arranged in a lattice pattern in the liquid crystal display panel 103. The gate driver 102 drives the gates of these pixels, and selects pixels where data is displayed. Incidentally, the gate driver 102 has the same number of outputs as the number of rows of pixels of the liquid crystal display panel 103. The source driver 101 turns on selected pixels in desired colors in accordance with display data by applying voltages that change based on the display data to the sources of the selected pixels. Incidentally, the source driver 101 has the same number of outputs as the number of columns of pixels of the liquid crystal display panel 103.
Furthermore, the source driver 101 includes a data driving portion 104, a drive voltage control circuit 105, and a switching signal generating portion 106. The data driving portion 104 generates voltage, which is applied to the pixels selected by the gate driver 102, from the data to be displayed. The drive voltage control circuit 105 generates voltage to drive the pixels based on the outputs from the data driving portion 104 and switching signal generating portion 106. The switching signal generating portion 106 generates one-shot pulses based on the horizontal synchronizing signal Hsync.
FIG. 10 shows a timing chart of the operation of the driving device 100 in the related art. Incidentally, FIG. 10 shows the outputs of the gate driver only for four rows, and the output of the source driver only for one column. As shown in FIG. 10, the gate driver 102 selects one row of pixels at each of the timings T10-T16. The drive voltage control circuit 105 of the source driver 101 generates a drive signal for each of the selected row of pixels. This drive signal has voltage equivalent to the sum of the output of the data driving portion and the switching signal (one-shot pulse), which is generated at the timing when the output of the data driving portion starts to change. That is, the output of the drive voltage control circuit 105 has a higher voltage value over a certain period Ta, which starts at the timing when the output of the data driving portion starts to change.
In this manner, it enables the signal to change more rapidly at the phase where the driving of pixels starts. That is, it can change the voltage that is applied to pixels by the source driver 101 to a predetermined voltage at earlier timing. By stabilizing the drive voltage more rapidly, it can drive a larger number of pixels in a short time. This fact becomes more effective when it drives a high definition liquid crystal display panel having a larger number of pixels.
Meanwhile, the desire to drive a liquid crystal display panel with low power consumption has been growing in recent years. Especially, the desire to reduce power consumption during the operation mode of a liquid crystal display panel that is mounted on a mobile device has been growing. However, there is a problem in the driving device 100 in the related art that since the drive voltage at the timing when the driving of pixels starts is higher than the required voltage in accordance with the display data, the power consumption by this part of circuit becomes larger.
Furthermore, since the drive voltage at the timing when the driving of pixels starts needs to be higher than the required voltage in accordance with the display data, the operating power supply voltage also needs to be higher in the driving device 100 in the related art. This imposes another problem that when the operating power supply voltage becomes higher, the power consumption of the drive voltage control circuit 105 also becomes higher.